Catalytic oxidation of organic nitrogen containing compounds

ABSTRACT

A method of treating a gaseous stream containing one or more volatile nitrogen containing organic compounds which comprises contacting the gaseous stream and an oxidizing agent with a catalyst at relatively low temperatures to cause oxidation of the volatile nitrogen-containing organic compounds. The catalyst employed promotes the oxidation reaction to selectively produce N 2  O, N 2 , CO 2  and H 2  O without generating significant amounts of NO x  to permit the reaction products to be vented directly into the atmosphere. The catalyst includes a selected amount of a noble or base metal deposited on a catalyst support comprising titania and zirconia. One or more of the elements molybdenum, tungsten or vanadium are added as promoters to the composition which minimizes the generation of NO x  among the reaction products. Lanthanum may be added to provide better thermal stability and increase the selectivity for producing N 2  among the reaction products. The process is effective when the gas stream also includes other non-nitrogen containing organic compounds or NO x  mixed with the nitrogen organic compound being treated without generating significant amounts of NO x  in the reaction products.

This application is a continuation under 37 CFR § 1.60 of priorapplication Ser. No. 08/505,800 filed Jul. 21, 1995.

TECHNICAL FIELD

The present invention relates generally to catalytic oxidation processesand particularly to the catalytic oxidation of gaseousnitrogen-containing compounds typically present in industrial off-gasstreams.

BACKGROUND ART

Volatile nitrogen-containing organic compounds, referred to herein as"VNC's", such as amines and nitrites, for example, must be removed fromindustrial off-gas streams prior to venting the gas stream into theatmosphere. Thermal incineration and catalytic oxidation are twodestructive methods which may be used for controlling off-gas emissions.Thermal incineration of off-gas streams containing VNC's generates boththermal and chemical nitrogen dioxide (NO₂) and nitric oxide (NO)(hereinafter referred to collectively as NO_(x)) which are the mostprevalent forms of nitrogen oxide present in measurable quantities inthe atmosphere.

Thermal generated NO_(x) gases are the result of oxidation of nitrogen(N₂) and occurs at high operating temperatures, while chemical generatedNO_(x) gases result from reactions involving the atomic nitrogenassociated with volatile nitrogen containing compounds.

It is well known that NO_(x) gases are a leading constituent of smog andacid rain. Further, they have been linked to depletion of stratosphericozone. While these gases are produced from natural sources, manmadesources can result in higher than desirable concentrations and thereforecontrol of these emissions is desirable. The use of thermal incinerationto decompose VNC's requires a costly NO_(x) abatement process to beemployed to control the NO_(x) emissions.

Catalytic oxidation process for decomposition of VNC's have theadvantage of operating at much lower temperatures than incinerationprocesses and thus remove the mechanism to generate thermal NO_(x).However, there is still the potential to produce chemical NO_(x) due tothe nitrogen associated with the VNC's. Recent studies by Lester andHomeyer presented at the 1993 Meeting of the American Chemical Societyin Denver, Colo. have reported the catalytic oxidation of a number ofVNC's over proprietary supported platinum catalyst on behalf of AlliedSignal Inc. This catalyst was able to readily destroy the VNC's tested;however significant quantities of NO_(x) were generated. Therefore, useof this catalyst in a process to destroy VNC's would also require anadditional abatement treatment of the NO_(x) gases generated.

Kuwabara, et al (Chem. Lett., 1992) describe the use of copper-exchangedzeolites as catalysts to oxidatively destroy trimethylamine without theformation of significant amounts of NO_(x). The apparently mostsuccessful catalyst used was a copper containing ZSM-5 which is acrystalline molecular sieve. However, such a catalyst is subject topoisoning by sulphur or halogen compounds often found in industrialoff-gas streams. Further, crystal and zeolite molecular sieves arerelatively costly to prepare for industrial applications.

A 1993 article by Rosenburg et al. provides an overview of selectivecatalytic reduction of NO_(x) emissions involving the addition ofammonia to a NO_(x) stream in the presence of a catalyst consisting ofvanadium supported on titania. These processes are useful to controlNO_(x) emissions with the addition of ammonia being necessary. However,this process is not useful to oxidatively destroy the VNC's without theformation of NO_(x).

There is a need to develop improved catalytic oxidation processescapable of destroying VNC's which do not generate NO_(x) emissions andthereby do not require further costly NO_(x) abatement operations suchas the one described in Rosenburg et al.

BRIEF DISCLOSURE OF INVENTION

The present invention relates to a process where oxidatively decomposingVNC's without producing significant amounts of NO_(x) emissions. Theprocess of the present invention comprises catalytically oxidizing VNC'susing a catalyst which includes a noble or base metal deposited on acatalyst support comprising zirconia or titania and promoted byadditions of vanadium, molybdenum or tungsten in the presence of anoxidizing agent. Lanthanum is a preferred addition for thermalstabilization of the catalyst.

More particularly, a gaseous stream containing one or more VNC's ispassed through a catalyst bed at a selected temperature range to obtainan oxidation reaction which selectively produces CO₂, H₂ O, N₂, N₂ O andtrace amounts, if any, of NO_(x) products. The process may be operatedat temperatures ranging from 200° to 500° C. depending upon theparticular composition of the catalyst described above, the residencetime and the particular constituents present in the incoming gas streamas well as the concentration thereof.

Further, the process according to the present invention also iseffective to decompose VNC's in a gas stream which include certaingaseous hydrocarbons or NO_(x), or a mixture thereof, wherein thecompounds are reacted without producing significant amounts of NO_(x),and the NO_(x) component in the feedstream is reduced.

Therefore, the processed and catalyst composition employed in accordancewith the present invention can effectively decompose VNC's at relativelylow operating temperatures without generating NO_(x) in any significantamounts to permit control of VNC's and NO_(x) emissions into theatmosphere in an economical manner which does not need a separate andcostly NO_(x) abatement operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a table showing the reaction products of a process accordingto the present invention decomposing hydrogen cyanide as a function oftemperature using the method described in Example II over a selectedtemperature range.

DETAILED DESCRIPTION

The present invention relates to a novel catalytic oxidation process tocontrol VNC emissions from industrial off-gas streams vented into theatmosphere without generating significant amounts of NO_(x). The processaccording to the present invention employs a catalyst composition whichcomprises a nobel or base metal supported on titania or zirconia and maybe promoted with selected amounts of molybdenum, tungsten or vanadium.This catalyst composition has been discovered to possess the ability toeffectively destroy VNC's in oxidizing environments without generatingsignificant NO_(x) emissions over selected relatively low temperatureranges.

In general, effective catalyst compositions contain about 0.03% to 5% ofa nobel metal or about 0.1% to 10% of a base metal which is impregnatedonto either a titania or zirconia support. Between about 1% to 20% ofmolybdenum, tungsten or vanadium, or a combination thereof, is added asa promoter of the selective oxidation reaction and about 1% to 7%lanthanum is a preferred addition to promote thermal stability of thecatalyst and appears to enhance the selectively towards the formation ofnitrogen among the reaction products. All percentages of catalystcomponents expressed herein are on a weight basis of the totalformulation unless otherwise specifically designated.

A preferred catalyst formula contains between 0.1% to 3% of a noblemetal, such as palladium or platinum, and between 3% to 7% vanadiumimpregnated onto a titania support which forms the balance of theformulation. It is more preferred to include between 1% to 5% lanthanum.Tungsten can be substituted for vanadium or molybdenum but is lesspreferred than either of these components in the formulation. Thecatalyst may be used in any configuration or size which sufficientlyexposes the catalyst to the gas stream being treated. Preferably, thetitania or zirconia support possesses a high surface area to obtainbetter dispersion of the components of the catalyst. The catalyst may beconfigured in many typical and well known forms such as, for example,pellets, granules, rings, spheres or cylinders, or may take the form ofa coating on an inert carrier, such as spheres or monoliths. Themonolithic form may be preferred when it is desired to reduce thepressure drop through the system or minimize attrition or dusting.

The catalytic components may be dispersed onto either the titania orzirconia support by means well known to the art. In general, it isdesired that the promoters be impregnated onto the support first,followed by impregnation of the noble or base metals. For example,molybdenum, tungsten or vanadium, or a combination of these, may bedispersed onto either the titania or zirconia support by impregnatinggranules with a solution containing one or both of these compounds.Following impregnation the granules may be dried and/or calcined at thedesired temperatures then impregnated with a solution containing a baseor noble metal. In both instances, the solution may be either aqueous ornonaqueous. Once the impregnation step is completed the resultingcatalyst may be dried and/or calcined.

When it is desired to add lanthanum to the catalyst, lanthanum may beadded to the solution containing the molybdenum, tungsten and/orvanadium. Alternatively, the lanthanum impregnation may be performedeither prior to or following impregnation with molybdenum, tungstenand/or vanadium.

If a monolithic form of the catalyst is desired, a slurry or solution oftitania, zirconia, titania plus promoters, or zirconia plus promotersmay be first coated onto the monolith by means well known to the art. Itis desirable that the amount of support material plus the promoterscoated onto the monolith be in the range of about 25 to 350 g/liter. Thenoble or base metal can be added in any convenient manner to the othercomponents, but preferably is added last using well known conventionalmeans to accomplish uniform impregnation of the metal onto the coatedmonolithic support.

The process involves passing a gas stream containing VNC's plus anoxidizing agent, such as air, through a catalyst bed consisting of thecatalyst described herein. The flow rates through the system should besufficient to allow for greater than at least 90% and preferably greaterthan 95% destruction of the VNC's and any other undesirable compounds ofinterest. Thus, the Gas Hourly Space Velocity (GHSV) can varysignificantly over a range of about 1,000 to about 300,000 hours⁻¹ andpreferably over a range of about 5,000 to 60,000 hours⁻¹.

The process described according to the present invention is alsoapplicable to the injection of liquid nitrogen-containing compounds intoa gas stream consisting of inert compounds plus an oxidizing agent airfor example. The gas stream flow rate and temperature and rate of liquidinjection are such as to allow for the vaporization of thenitrogen-containing compounds. The gas stream containing the vaporizednitrogen-containing compounds is then contacted with the catalystdescribed herein.

It should be noted that in the formulation of the catalyst, thecomponents, particularly the noble or base metal should be highlydispersed throughout the particular configuration used. The degree ofmetal dispersion can effect the efficiency of the chemical reactiondesired. Further, the dispersion of the components on the form used canalso effect the temperature range and the residence time required toobtain the desired conversion percentage of the VNC's being treated.Alternatively, the better dispersion of the metals can reduce thequantity of the components needed to achieve a given efficiency of thereaction at the same operating temperature and residence time. It shouldalso be noted that after the gas stream has been treated in accordancewith the present invention, further treatment, if desired, may beeffected to remove the smaller quantities of N₂ O which may be requiredto achieve the future emission standard. Also, halogen containingorganic compounds included in the gas stream, including those containingatomic nitrogen, also can be oxidized in accordance with the presentinvention resulting in the production of acid gases. If theconcentration of such acid gases in the exiting gas stream are deemedunacceptable, conventional collection or abatement processes may beemployed to avoid venting acid gases directly into the atmosphere.

The reaction temperature range within which the process is operated isbased on a number of factors which include the concentration of thetarget VNC to be decomposed, the reactivity level of the target VNC, thespace velocity and the percentage of the noble or base metal associatedwith the catalyst. Generally, lower operating temperatures may beemployed for VNC compounds which are readily oxidized by the catalyst orfor those present in relatively low concentrations in the incoming gasstream, less than about 500 ppm for example. Further, the operatingtemperature may be reduced by decreasing the space velocity of theincoming gas stream and/or increasing the percentage of the base fornoble metal component associated with the catalyst.

It should also be pointed out that the process parameter is noted hereinwhich include varying the composition of the catalyst with respect tothe percentages of the promotor elements, such as molybdenum, tungsten,and vanadium for example, also alter the selectivity of thenitrogen-containing reaction products generated. This provides one theability to design the process to achieve the most desirable result whenactual operation in a particular industrial application tends to setcertain limits on certain process parameters. Using certain catalystcompositions demonstrate, for example, that selectively producing verylow percentages of NO_(x) occur within a given temperature range andtherefore higher or lower operating temperatures need to be avoidedunless other operating parameters are appropriately adjusted, such asspace velocity for example. The relatively wide range of suitableoperating conditions which produce useful results is a significantadvantage in using the process according the present invention.

It should also be noted that since oxidation reaction of the VNC's areexothermic, the temperature of the incoming gas stream can be treatedshould be adjusted to take into account the potential for the reactiontemperature at the catalyst bed to be higher due to the heat generatedby the chemical reactions so that the catalyst temperature does notexceed a level such that NO₂ formation becomes significant.

The composition of the catalyst reported in the following examples ofthe present invention is stated in percent by weight and was calculatedbased upon the elements described in the catalyst. Therefore, anappropriate amount of a salt is used so that the weight percent of themetal component derived from the salt is included in the catalyst asdescribed in the examples. When the solution of the salt is evaporated,the salt remains associated with the titania or zirconia support untilcalcination. At this point, the salts convert into metal and/or metaloxides. No formal analysis, such as atomic absorption, was performed toobtain an accurate measure of the catalyst composition. In view of therelatively wide range of catalyst formations found to be operable withinthe general ranges disclosed, highly precise determinations of thecatalyst determinations were not deemed necessary.

The selectivity of the nitrogen-containing reaction products is notedherein and calculated on the basis of the available atomic nitrogenpresent in the VNC in the incoming stream.

The concentrations of CO₂, N₂ O, and N₂ in the reactor effluent in thefollowing examples described herein were determined using gaschromatographic techniques which employed packed columns to perform theseparation and a thermal conductivity detector to quantitativelydetermine the product concentration. The concentration of VNC in thefeed and effluent streams was determined using gas chromatographictechniques which employed a packed column to perform the separation. Aflame ionization detector was used to provide quantitative analysis. Theconcentration of NO_(x) and the reactor effluent was determined using achemiluminescent NO/NO_(x) analyzer which employed an optical filter andphotomultiplier. These analytical techniques are well known to thoseskilled in the art.

Further, the addition of the promoters to the catalyst compositiondescribed herein have a slight retarding effect on the catalyticactivity; however, these components have been found to dramaticallyminimize NO_(x) formation in the process according to the presentinvention. Also, the inclusion of a noble or base metal in the catalystcomposition not only significantly enhances the reactivity of thecatalyst, but further dramatically minimizes the formation of NO_(x) inthe reaction products. If either the noble or base metal promotersdescribed herein are omitted from the catalyst composition, thegeneration of NO_(x) and the reaction products is increased severalhundred fold or the oxidation of the VNC is decreased several hundredfold under the same processing conditions. Therefore, both of theseconstituents are required in the catalyst composition and cooperate toachieve the improved results of effectively decomposing VNC's whileminimizing generation of NO_(x) among the reaction products. In view ofthe above description and examples of the process according to thepresent invention which follow, it should be understood by those skilledin the art that the present invention provides a process and catalystformulation which very effectively destroys VNC's without generatingsignificant amounts of the undesirable NO_(x) gases. Further, thecatalyst formulations disclosed herein are not readily subject topoisoning many organic compounds which may be present in a wide varietyof industrial off-gas applications. The economic impact of such aprocess which does not require costly additional NO_(x) abatementoperations represents a novel and valuable contribution to the state ofthe art.

EXAMPLE I

A catalyst was prepared on a weight basis containing nominally 1%platinum, 5% vanadium and 5% lanthanum with the balance titania asfollows: 25 g of primarily anatase phase titania (Degussa p-25) with asurface area of approximately 50 m² /g was slurried into 250 mldistilled, deionized water. To the slurry was added 2.9 g lanthanumnitrate hydrate dissolved in 30 ml distilled water. The slurry was thenplaced in a rotary evaporator at 45° C. and the water was evaporatedfrom the slurry overnight. The remaining solid was dried at 125° C. forstet hours, then crushed and sieved to 25/60 mesh granules. The granuleswere then calcined at 450° C. for four hours. Approximately 8 g of theresulting granules were slurried in 200 ml distilled, deionized water.To the slurry was added approximately 0.9 g ammonium metavanadatedissolved in 80 ml distilled, deionized water. The slurry was thenplaced in a rotary evaporator at 60° C. and the water was evaporatedovernight. The remaining solids were dried at 125° C. for two hours thencalcined at 450° C. for four hours. Approximately 2.0 g of the resultinggranules were slurried in 50 ml distilled deionized water. Then, 0.04 gtetramineplatinum nitrate dissolved in 25 ml distilled, deionized waterwas added to the slurry. The slurry was placed in a rotary evaporator at60° C. and the water was evaporated overnight. The resulting materialwas dried at 125° C. for two hours, then reduced in a hydrogenenvironment for two hours at 450° C., then calcined at 450° C. for twohours. Approximately one gram of the resulting material containingnominally 1% Pt, 5% V, 5% La supported on TiO₂ was exposed to 2000 ppm(v\v) hydrogen cyanide in 21% O₂ \He following at 200 ml/min at 350° C.At this temperature, the conversion of hydrogen cyanide was greater than99.95%. The reaction product distribution consisted of 8 ppm NO_(x), 100ppm N₂ O, 970 ppm N₂ and 2,100 parts per million CO₂. No carbon monoxideor products of partial oxidation were detected.

EXAMPLE II

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with the balance titania as follows: Approximately 2.0 g ofthe granules prepared containing (nominally) 5% vanadium, 5% lanthanumwith the balance titania according to Example I were slurried in 50 mldistilled, deionized water. Approximately 0.05 g tetraaminepalladiumchloride dissolved in 10 ml distilled, deionized water was added to theslurry. The slurry was placed in a rotary evaporator at 60° C. and thenwas evaporated overnight. The resulting material was dried at 125° C.for two hours then reduced in a hydrogen environment at 450° C. for twohours then calcined at 450° C. for two hours. Approximately one gram ofthe resulting material containing nominally 1% Pd, 5% V, 5% La supportedon TiO₂ was exposed to 2,000 ppm (v\v) hydrogen cyanide and 21% O₂ \Heflowing at 200 ml/min. The catalyst was exposed to the feed streamdescribed at temperatures between 350° C. and 450° C. The concentrationof the reaction products formed at ten degree intervals are listed inFIG. 1. In the temperature range between 350° C. to 420° C., greaterthan 99.95% of the hydrogen cyanide was destroyed without generation ofmore than five parts per million of NO_(x). The catalyst was thenexposed to 2,000 ppm hydrogen cyanide continuously for 24 hours at 370°C. The conversion of hydrogen cyanide was greater than 99.95% throughoutthe duration of the run. The NO_(x) selectivity was less than 1%throughout the duration of the run.

EXAMPLE III

A catalyst was prepared containing nominally 5% chromium, 5% vanadium,5% lanthanum with the balance of titania as follows: Approximately 2.0 gof the (nominally) 5% V/5% La/TiO₂ granules prepared according toexample I where slurry in 50 ml distilled, deionized water.Approximately 0.76 g chromium nitrate nonahydrate dissolved in 25 mldistilled, deionized water was added to the slurry. The slurry wasplaced in a rotary evaporator at 60° C. and the water was evaporatedovernight. The resulting material was dried at 125° C. for two hours,then reduced in a hydrogen environment at 450° C. for two hours, thencalcined at 450° C. for two hours. Approximately one gram of theresulting material containing nominally 5% Cr, 5% V, 5% La supported onTiO₂ was exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /Heflowing at 200 ml/min at 400° C. At 400° C., the conversion of hydrogencyanide was greater than 99.95%. The reaction product distributionconsisted of 19 ppm NO_(x), 560 ppm N₂ O, 585 ppm N₂ and 2,250 ppm CO₂.No carbon monoxide or products of partial oxidation were detected atthis temperature.

EXAMPLE IV

A catalyst was prepared containing nominally 1% palladium, 3% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 350° C. At 350° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 7ppm NO_(x), 75 ppm N₂ O, 950 ppm N₂ and 2,285 ppm CO₂. No carbonmonoxide or products of partial oxidation were detected at thistemperature.

EXAMPLE V

A catalyst was prepared containing nominally 1% palladium, 7% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 350° C. At 350° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 11ppm NO_(x), 221 ppm N₂ O, 750 ppm N₂ and 2,275 ppm CO₂. No carbonmonoxide or products of partial oxidation were detected at thistemperature.

EXAMPLE VI

A catalyst was prepared containing nominally 1% palladium, 5% vanadiumwith a balance titania in a manner similar to that described previously.Approximately one gram of the resulting material was exposed to 2,000ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at 200 ml/min at 350°C. and 400° C. At 400° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 3.9ppm NO_(x), 275 ppm N₂ O, 725 ppm N₂ and 2,200 ppm CO₂. At 350° C., theconversion of hydrogen cyanide was greater than 99.95%. The reactionproduct distribution consisted of 4.1 ppm NO_(x), 350 ppm N₂ O, 675 ppmN₂ and 2,200 ppm CO₂. No carbon monoxide or products of partialoxidation were detected at either temperature.

EXAMPLE VII

A catalyst was prepared containing nominally 0.1% palladium, 5%vanadium, 5% lanthanum with a balance titania in a manner similar tothat described previously. Approximately one gram of the resultingmaterial was exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /Heflowing at 200 ml/min at 400° C. At 400° C., the conversion of hydrogencyanide was greater than 99.95%. The reaction product distributionconsisted of 2.6 ppm NO_(x), 200 ppm N₂ O, 665 ppm N₂ and 1,825 ppm CO₂.No carbon monoxide or products of partial oxidation were detected ateither temperature.

EXAMPLE VIII

A catalyst was prepared containing nominally 3% palladium, 5% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 350° C. At 350° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of lessthan 0.5 ppm NO_(x), 135 ppm N₂ O, 800 ppm N₂ and 2,025 ppm CO₂. Nocarbon monoxide or products of partial oxidation were detected at thistemperature.

EXAMPLE IX

A catalyst was prepared containing nominally 1% palladium, 7% molybdenumwith a balance titania in a manner similar to that described previously.Approximately one gram of the resulting material was exposed to 2,000ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at 200 ml/min at 330°C. and 370° C. At 370° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 2.1ppm NO_(x), 60 ppm N₂ O, 825 ppm N₂ and 1,950 ppm CO₂. At 330° C., theconversion of hydrogen cyanide was greater than 99.95%. The reactionproduct distribution consisted of 5.8 ppm NO_(x), 100 ppm N₂ O, 850 ppmN₂ and 2,000 ppm CO₂. No carbon monoxide or products of partialoxidation were detected at either temperature.

EXAMPLE X

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) diethylamine in 21% O₂ /He flowing at 200ml/min at 350° C. At 350° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 7.8ppm NO_(x), 120 ppm N₂ O, 850 ppm N₂ and 7,700 ppm CO₂. No carbonmonoxide or products of partial oxidation were detected at eithertemperature.

EXAMPLE XI

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 380° C. and 320° C. At 380° C., the conversion of hydrogencyanide was greater than 99.95%. The reaction product distributionconsisted of 50 ppm NO_(x), 100 ppm N₂ O, 600 ppm N₂ and 1,950 ppm CO₂.At 320° C., the conversion of hydrogen cyanide was greater than 99.95%.The reaction product distribution consisted of less than 0.5 ppm NO_(x),80 ppm N₂ O, 500 ppm N₂ and 1,820 ppm CO₂. No carbon monoxide orproducts of partial oxidation were detected at either temperature.

EXAMPLE XII

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with a balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 750 ppm NO₂ in 21% O₂/He flowing at 200 ml/min at 350° C. and 390° C. At 390° C., theconversion of hydrogen cyanide was greater than 99.95%. Theconcentration of nitrogen and carbon species in the reactor effluent wasas follows: 21 ppm NO_(x), 175 ppm N₂ O, 1,150 ppm N₂ and 2,200 ppm CO₂.At 350° C., the conversion of hydrogen cyanide was greater than 99.95%.The concentration of nitrogen and carbon species in the reactor effluentwas as follows: less than 0.5 ppm NO_(x), 100 ppm N₂ O, 1.225 ppm N₂ and2,175 ppm CO₂. No carbon monoxide or products of partial oxidation weredetected at either temperature. Results demonstrate that the catalystand process are capable of reducing NO_(x) in a process streamcontaining NO_(x) hydrogen cyanide and oxygen.

EXAMPLE XIII

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with the balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 500 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 310° C. and 350° C. At 350° C., the conversion of hydrogencyanide was greater than 99.95%. The reaction product distributionconsisted of 3.9 ppm NO_(x), 25 ppm N₂ O, 210 ppm N₂ and 475 ppm CO₂. At310° C., the conversion of hydrogen cyanide was approximately 99.95%.The reaction product distribution consisted of 5.1 ppm NO_(x), 27 ppm N₂O, 200 ppm N₂ and 465 ppm CO₂. No carbon monoxide or products of partialoxidation were detected at these reaction temperatures.

EXAMPLE XIV

A catalyst was prepared containing nominally 1% palladium, 10% vanadium,5% lanthanum with the balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at200 ml/min at 340° C. and 400° C. At 400° C., the conversion of hydrogencyanide was greater than 99.95%. The reaction product distributionconsisted of 9 ppm NO_(x), 140 ppm N₂ O, 775 ppm N₂ and 2,100 ppm CO₂.At 340° C., the conversion of hydrogen cyanide was approximately 99.95%.The reaction product distribution consisted of less than 0.5 ppm NO_(x),170 ppm N₂ O, 650 ppm N₂ and 2,100 ppm CO₂. No carbon monoxide orproducts of partial oxidation were detected at these reactiontemperatures.

EXAMPLE XV

A catalyst was prepared containing nominally 5% iron, 5% vanadium, 5%lanthanum with the balance titania in a manner similar to that describedpreviously. Approximately one gram of the resulting material was exposedto 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at 200 ml/minat 400° C. At 400° C., the conversion of hydrogen cyanide was greaterthan 99.5%. The reaction product distribution consisted of 15.3 ppmNO_(x), 200 ppm N₂ O, 600 ppm N₂ and 2,100 ppm CO₂. No carbon monoxideor products of partial oxidation were detected at this reactiontemperature.

EXAMPLE XVI

A catalyst was prepared containing nominally 5% nickel, 5% vanadium, 5%lanthanum with the balance titania in a manner similar to that describedpreviously. Approximately one gram of the resulting material was exposedto 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at 200 ml/minat 400° C. At 400° C., the conversion of hydrogen cyanide was greaterthan 99.95%. The reaction product distribution consisted of 6.8 ppmNO_(x), 210 ppm N₂ O, 650 ppm N₂ and 2,125 ppm CO₂. No carbon monoxideor products of partial oxidation were detected at this reactiontemperature.

EXAMPLE XVII

A catalyst was prepared containing nominally 1% palladium, 5% vanadium,5% lanthanum with the balance titania in a manner similar to thatdescribed previously. Approximately 0.87 g of the resulting material wasexposed to 2,000 ppm (v/v) cyanogen chloride in 21% O₂ /He with 1.5% H₂O (v/v) flowing at 175 ml/min at 200°, 300° and 400° C. At 200° C., theconversion of cyanogen chloride was greater than 99.9%. The reactionproduct distribution consisted of 20 ppm NO_(x), less than 5 ppm N₂ O,965 ppm N₂ and 1,950 ppm CO₂. At 300° C., the conversion of cyanogenchloride was greater than 99.9%. The reaction product distributionconsisted of 145 ppm NO_(x), less than 5 ppm N₂ O, 900 ppm N₂ and 1,950ppm CO₂. At 400° C., the conversion of cyanogen chloride was greaterthan 99.9%. The reaction product distribution consisted of 240 ppmNO_(x), 200 ppm N₂ O, 575 ppm N₂ and 1,950 ppm CO₂. No carbon monoxideor products of partial oxidation were detected at these reactiontemperatures. No determination or measurement was made of aconcentration of Hcl, which was present in the exiting treated gasstream.

EXAMPLE XVIII

A catalyst was prepared containing nominally 1% palladium, 3% tungsten,5% lanthanum with the balance titania in a manner similar to thatdescribed previously. Approximately one gram of the resulting materialwas exposed to 2,000 ppm (v/v) hydrogen cyanide in 21% O₂ /He flowing at100 ml/min at 340° C. At 340° C., the conversion of hydrogen cyanide wasgreater than 99.95%. The reaction product distribution consisted of 75ppm NO_(x), 85 ppm N₂ O, 800 ppm N₂ and 2,100 ppm CO₂. No carbonmonoxide or products of partial oxidation were detected at eithertemperature.

It should be noted that other formulations of the catalyst used withinthe parameters described herein could be successfully employed in theprocess according the present invention as well as choosing otheroperating parameters to meet a given application and level ofeffectiveness suitable to the application without departing from thespirit of the present invention. The selective oxidation achieved toproduce the lower levels of NO_(x) generated in the reaction products isgenerally most desirable. This selectivity of the components formed bythe oxidation reactions which can readily reduce the amount of NO_(x) inthe exiting treated gas stream represents a significant advantage overprior abatement processes used to treat VNC ladened gas streams.

We claim:
 1. A catalyst for the catalytic oxidation of VNC's withlimited production of NO_(x) compounds, said catalyst comprising:atleast one compound selected from the group consisting of titanium oxideand zirconium oxide, from about 1% to about 20% by weight of an elementselected from the group consisting of molybdenum, tungsten, andvanadium, from about 0.03% to about 5% by weight of a metal selectedfrom the group consisting of platinum or palladium, and from about 1% toabout 10% by weight lanthanum.
 2. The catalyst of claim 1, wherein saidmetal is present in an amount from about 0.1% to about 3% by weight. 3.The catalyst of claim 1, wherein said element is vanadium and is presentin an amount from about 3% to about 7% by weight vanadium.
 4. A catalystfor treating gaseous streams containing VNC's with reduced production ofNO_(x) compounds, said catalyst comprising:from about 0.1% to about 3.0%by weight of a noble metal; from about 3.0% to about 7% by weightvanadium; and titania.
 5. The catalyst of claim 4, wherein said noblemetal is selected from the group consisting of platinum and palladium.6. The catalyst of claim 4, further comprising zirconia.
 7. A catalystfor treating VNC's in a gaseous stream with limited production of NO_(x)compounds, said catalyst comprising:a base or noble metal; an elementselected from the group consisting of vanadium, molybdenum, andtungsten; and a support comprising zirconia.
 8. The catalyst of claim 7,wherein the noble metal is selected from the group consisting ofplatinum and palladium.
 9. The catalyst of claim 7, wherein the noblemetal is present in an amount from about 0.03% to about 5% by weight.10. The catalyst of claim 7, wherein the base metal is selected from thegroup consisting of chromium, iron, and nickel.
 11. The catalyst ofclaim 7, wherein the base metal is present in an amount from about 0.1%to about 10% by weight.
 12. The catalyst of claim 7, wherein saidelement is present in an amount from about 1% to about 20% by weight.13. The catalyst of claim 7, further comprising lanthanum.
 14. Thecatalyst of claim 7, wherein said support further comprises titania. 15.The catalyst of claim 7, wherein said element is vanadium.